DESCRIPTION: Training Plan: The candidate will study, H. pylori, a bacterium that chronically infects the gastric mucosa, and is associated with the development of peptic ulcer disease and gastric malignancy. The candidate proposes to test the hypothesis that virulence determinants in H. pylori may be regulated by growth phase using the non-essential sigma subunit of RNA polymerase, RpoS. The rpoS homologue from H. pylori will be cloned and molecularly characterized. An isogeneic RpoS-negative mutant will be constructed by transposon mutagenesis with allelic exchange characterized. These studies will contribute to our understanding of H. pylori pathogenesis, and may suggest novel strategies for therapeutic intervention or vaccine development.